A touch panel is a pointing device that detects an input operation when an operator's finger or a dedicated stylus/pen is brought into close proximity to an input operation area on the surface and outputs the detected positional information to a host electronic device in which the touch panel is mounted. A touch panel is usually arranged on the front side of a display panel such as a liquid crystal panel or a CRT. When an input operation is performed as guided by the contents on the display panel, the location of the input operation is output to the electronic device in connection with the displayed contents.
Various types of touch panels that detect the location of an input operation are known, such as magnetic coupling, capacitive, and resistive touch panels. Since touch panels can locate the position of an input operation from a slight touch in an input operation area, the operator sometimes cannot recognize whether or not the input operation to the touch panel has been accepted and feels uncertain about the input operation. A new type of touch panel called force feedback touch panel has been developed, which vibrates itself and allows the operator to feel the vibration via a dedicated stylus/pen or a fingertip in contact with the input operation area so as to let the operator know that an input operation to the touch panel has been detected. The applicant of the present invention has developed a force feedback touch panel that has a piezoelectric substrate fixedly and directly attached to the touch panel as an oscillatory element, so that the touch panel has a compact design and can vibrate itself efficiently (Patent Document 1).
However, when the touch panel, which vibrates itself, is attached fixedly to the case of an electronic device, the vibration is restricted by the case and may not fully be sensed by the operator. Accordingly, the applicant of the present invention has developed a touch panel support structure for mounting a touch panel, which has a fixedly attached piezoelectric substrate as an oscillatory element, to a case via a resilient support frame (Patent Document 2).
This conventional touch panel support structure 100 will be described below with reference to FIG. 12. As shown in the drawing, the touch panel 102 having a pair of piezoelectric elements 101 firmly attached along the side edges on the back side is fitted, with a display panel 103, into and supported by a resilient support frame 104 formed in a rectangular frame shape. The resilient support frame 104 includes an integrally formed panel receiving portion 104a that extends all around the inner wall and protrudes horizontally inwards. The frame further includes integrally formed touch panel supports 104b at four corners of the panel receiving portion 104a on the front side. The touch panel 102 is supported at four corners on the touch panel supports 104b on the front side of the panel receiving portion 104a, while the display panel 103 is supported on the back side, so that the touch panel 102 is supported in parallel and above (on the front side of) the display panel 103.
The resilient support frame 104 with the touch panel 102 and the display panel 103 attached in position is secured to the edges of an opening 105a in the housing 105 of the electronic device, with the touch panel 102 exposed through the opening 105a. A transparent protective sheet 106 is then bonded over the touch panel 102 and around the opening 105a such as to cover the entire surface of the touch panel 102 and the surrounding of the opening 105a so as to prevent entrance of dust or moisture from the opening 105a. 
As the touch panel 102 is mounted to the housing 105 via the resilient support frame 104 that has resiliency, and is covered with a flexible transparent sheet 106 on the front side, the touch panel 102 can freely vibrate when the piezoelectric elements 101 are driven, so that the operator can feel the vibration upon touching the transparent protective sheet 106 for an input operation.